Be or not to be, that is the question?: The case of Equus neogeous (Equidae: Perissodactyla: Mammalia) as a Lujanian Stage/Age fossil guide from the Pleistocene deposits in South America

VEZZOSI, RAÚL I.; AVILLA, S.L.; BRUNETTO, ERNESTO

Córdoba

Jornada; 33º Jornadas de Paleontología de Vertebrados; 2019

CICTERRA-CONICET; FCEFYN-UNC

The chronology and continental biostratigraphy of the SA late Cenozoic are based on fossil mammals from Argentina. Especially, the reliability of the local biostratigraphical units lies on the authenticity of the stratigraphic position of the fossil mammals from the Pampean Region (BsAs) and the precision of its taxonomic studies. Consequently, the Equus neogeus biozone is the biostratigraphical Quaternary unit representative of the Lujanian Stage/Age, which corresponds to Late (latest) Pleistocene/Early (earliest) Holocene. Until now, paleontological contributions had been scarce, principally consisting of reports of isolated discoveries and preliminary groupings of mammals without a good stratigraphical context. However, the substantial number of geological and stratigraphical Pleistocene studies conducted in the last years have provided a useful basis for news hypothesis in South America. We discuss the biostratigraphical/chronological hypothesis that sets the species E. neogeus as the fossil guide for the chronological Pleistocene Series (Lujanian Stage/Age) in lowlands. E. neogeus is herein reported since the Middle Pleistocene (198?178 ±20.6 ka A.P., OSL LVD 2826, 2827) to Late Pleistocene from Northern Pampa (Santa Fe). In this sense, the records in a suitable stratigraphical context from Northern Pampa, clearly suggest an earlier occurrence at low latitudes by SA. The new records allow establishing that E. neogeus is not an accurate regional biostratigraphical indicator to the age Late Pleistocene sensu stricto. Therefore, the Lujanian Stage/Age should be interpreted as a local sequence for the BsAs and should not be extrapolated to a regional framework to define and compare lithostratigraphical sequences of Pleistocene age.